1. Field of the Invention
The present invention relates to a pattern position measuring apparatus for measuring the position of a pattern formed on a sample such as a mask and a reticle.
2. Related Background
Hitherto, when the position of a pattern formed on the surface of a sample such as a mask and a reticle adsorbed onto the stage is detected, an error committed in the result of the measurement of the pattern due to the distortion of the sample is corrected.
For example, a pattern position measuring apparatus has been disclosed in U.S. Pat. No. 4,730,927 which is arranged in such a manner that, whenever an edge of a pattern formed on the surface of a sample is detected, the slope of the surface of the sample at this position is calculated so as to correct the position of the pattern edge.
However, the above-described conventional technology is arranged in such a manner that, whenever the pattern edge is measured, the measuring point and the interval between a position in front of the measuring point and a position in rear of the same are measured so as to obtain the slope of the sample at the measuring point and correct the distortion. Therefore, there arises a problem in that, if a large number of measuring points are measured, an excessively long time is required to complete the measurement, causing the throughput of the apparatus to deteriorate.